I'm new to Space Engine, but OH MAN is this awesome - 0.97 is better still, and the options to customize planets and create your own are really fascinating.

I have a few suggestions that could be implemented, unless something like these are already planned and/or implemented.

First are glowing oceans - having more options with oceans would be handy. Having them emit their own light so the night side of the planet is illuminated by glowing liquid for various reasons would look really cool. It would also be a way to implement lava-planets, since rocky worlds orbiting really close to their star would probably have oceans of lava with islands of slightly more durable rock. One of the worlds in my personal universe is one with lakes that glow with bio-luminescence. Flora on this world glow as well. Another option I'd like for oceans is changeable opacity, unless I'm doing it wrong. I did say I'm new to Space Engine. I almost got a fake-glowing oceans effect by really jacking up the Exposure or DayAmbient or something, but it was only out to a certain distance. It looked cool, since it looked like it was a sea of white-hot glowing magma.

New planet classes would always be welcome. I heard something about lava worlds, the opposite of ice worlds that exist very close to their parent sun. Perhaps with an ocean of glowing lava that persists into the night side.

Chthonian planets would be neat, if anyone has any idea of what they would look like. It might be a sub-class of planets, one that would probably have a really young and unusual looking surface. These are gas giant planets that have their outer atmospheric layers blown away, leaving only the rocky core. The surface could emit its own heat because of it being the core of a former gas giant, and they might be in orbit around stellar remnants such as white dwarfs or neutron stars. I came across a gas giant planet that had its own comet tail in my interstellar journeys.

Carbon planets would be dense, very dark in color with an atmosphere that is dark and smoky. And it would have diamond protrusions and a high gravitational pull. Planets have been discovered with a significantly higher level of carbon compounds than our solar system.

Finally - sub-brown dwarfs as well as planet-like brown dwarfs of Y, T and L type. I tried adding rings to a brown dwarf and it didn't work. I tried to force it to work by adding a dummy planet in the center of the brown dwarf and it had lots of weird graphical quirks, but otherwise worked fairly well. Maybe there is another way to do this? In fact, a stellar ring system would make sense for developing solar systems, it would be neat to have a dusty ring around a young star with planetoids interspersed throughout. It could be rendered similarly to how galaxies are rendered, only on a much smaller scale.

The final suggestion I want to make is about dynamic elements.

First let's consider a planet that orbits a star with quite an eccentricity... such that at its perihelion the frozen nitrogen and other volatiles sublime and give the planet a much more significant atmosphere - to the point where liquid volatiles can form on the surface. We may not have planets that have such a dramatic change to their surface, but we do have planets that have changing atmospheres. Pluto, Triton, Titan possibly Eris and Sedna. Titan warms up enough to evaporate its lakes of hydrocarbons. Pluto has a slightly thicker atmosphere during its perihelion - as does Triton. Mars has a variable atmosphere as well. The simplest way to implement dynamic atmosphere is to increase the pressure at perihelion and decrease it at aphelion, there wouldn't be any surface changes. An atmosphere could have a variable opacity and height. Clouds could be more frequent at certain times of the year as well. Ocean level would change.

It may please you to know that several of your suggestions have already been discussed for future versions, though which ones will be implemented when remains to be seen of course. But I really like your detailed thoughts on such a wide range of features and how they could be rendered in SpaceEngine, and I hope SpaceEngineer will consider them. Ultimately the desire is for this program to be capable of representing all known astronomical phenomenon.

Lava and carbon worlds are high on my wishlist, along with protoplanetary systems.

Instead of having a seperate carbon class, perhaps the existing planet classes should have a carbon "flavor" that can be found in galactic centers, globular clusters, and other areas with different carbon:oxygen ratios. C-Selenas and C-ice worlds would look darker and sootier, C-Deserts would have a smoggy atmosphere, C-Terras would have oily tar oceans, and C-giants could have darker, more venus-like clouds.

There could even be carbon rich stars... in fact I believe any planet that is carbon rich would be in a system of carbon rich planets orbiting a carbon rich star.

Iron planets could be another class. In our solar system, Mercury could be considered an Iron planet, but even more extreme cases can exist out in space. According to Wikipedia, they could be kind of like Chthonian planets, only with terrestrial worlds, where the outer crust and mantle is stripped away from large impacts leaving only the iron core. It would also probably have fields of diamond.